U.S. patent application number 10/223544 was filed with the patent office on 2003-02-27 for method of sending a multicast message in such as a gprs/umts network, and a mobile telecommunications network.
Invention is credited to Casati, Alessio, Palat, Sudeep Kumar.
Application Number | 20030039232 10/223544 |
Document ID | / |
Family ID | 26077192 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030039232 |
Kind Code |
A1 |
Casati, Alessio ; et
al. |
February 27, 2003 |
Method of sending a multicast message in such as a GPRS/UMTS
network, and a mobile telecommunications network
Abstract
A method of sending a multicast message to a plurality of mobile
stations in a multicast group is provided. The method involves
sending to an access point of a mobile telecommunications network a
control message to assign a mobile station to a multicast group.
The multicast message is sent to each of one or more access points,
each having one or more associated mobile stations in the multicast
group. Each access point forwards the multicast message to its
associated one or more mobile stations in the multicast group.
Inventors: |
Casati, Alessio; (Wiltshire,
GB) ; Palat, Sudeep Kumar; (Wiltshire, GB) |
Correspondence
Address: |
Docket Administrator (Room 3J-219)
Lucent Technologies Inc.
101 Crawfords Corner Road
Holmdel
NJ
07733-3030
US
|
Family ID: |
26077192 |
Appl. No.: |
10/223544 |
Filed: |
August 19, 2002 |
Current U.S.
Class: |
370/337 ;
370/347; 370/349; 370/401 |
Current CPC
Class: |
H04W 76/40 20180201;
H04W 8/186 20130101; H04W 92/24 20130101; H04L 12/185 20130101;
H04L 12/189 20130101; H04W 92/02 20130101; H04L 12/1836
20130101 |
Class at
Publication: |
370/337 ;
370/347; 370/349; 370/401 |
International
Class: |
H04B 007/212; H04L
012/56 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 22, 2001 |
GB |
0120421.3 |
Nov 21, 2001 |
EP |
01309799.3 |
Claims
We claim:
1. A method of sending a multicast message to a plurality of mobile
stations, comprising: sending to an access point of a mobile
telecommunications network a control message to assign a mobile
station to a multicast group; and sending the multicast message to
the or each access point having one or more associated mobile
stations in the multicast group wherein the, or each said access
point forwards the multicast message to its associated one or more
mobile stations in the multicast group.
2. A method of sending a multicast message according to claim 1, in
which the control message is sent from an anchor point which is a
gateway GPRS support node upon receipt of a group membership
instruction from the mobile station.
3. A method of sending a multicast message according to claim 2, in
which the anchor point is operative to set up GPRS tunnelling
protocol (GTP) tunnels for the multicast group between the anchor
point and a signalling GPRS support node (SGSN), and between the
SGSN and the access point, or to add a mobile station identifier to
a membership list for the group if the GTP tunnels already
exist.
4. A method of sending a multicast message according to claim 1, in
which the network is a UMTS core network and the or each access
point is a radio network controller.
5. A method of sending a multicast message according to claim 1, in
which the mobile station is assigned to a multicast group by
sending signalling comprising a multicast access point name as part
of a create packet data protocol context set-up.
6. A method of sending a multicast message according to claim 1, in
which the control message indicates that the access point to a
mobile station is to join a multicast group so as to receive and
forward multicast messages to its associated mobile station(s) in
the multicast group.
7. A method of sending a multicast message according to claim 1, in
which the network is a UMTS core network, and the or each access
point is a radio network controller; and the control message is
sent from an anchor point which is a gateway GPRS support node upon
receipt of a group membership instruction from the mobile station;
and the control message indicates that a radio access bearer is to
be set up for multicast messaging to the mobile station.
8. A method of sending a multicast message according to claim 1, in
which upon a mobile station moving to the control of a new access
point, associated multicast group membership information is
forwarded to the new access point.
9. A method of sending a multicast message according to claim 1, in
which the network is a second generation GPRS core network, and the
access point is a signalling GPRS support node.
10. A mobile telecommunications network comprising a multicast
server operative to control the sending to an access point of the
telecommunications network of a control message to assign a mobile
station to a multicast group, and operative to control the sending
of a multicast message to each of one or more access points, the or
each access point having one or more associated mobile stations
assigned to the multicast group, and the or each access point being
operative to forward the multicast message to its associated one or
more mobile stations assigned to the multicast group.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority of Great Britain
Provisional Application No. 0120421.3 filed on Aug. 22, 2001 and
European Application No. 01309799.3 filed Nov. 21, 2001.
TECHNICAL FIELD
[0002] The present invention relates to a method of sending a
multicast message to a plurality of mobile stations in a multicast
group, and to a mobile telecommunications network comprising a
multicast server.
BACKGROUND OF THE INVENTION
[0003] There is a requirement in Universal Mobile
Telecommunications Systems (UMTS) standards to support multicast
services. The known solution is for the gateway general packet
radio system (GPRS) support node (GGSN), which is the point of
entry to the UMTS network, to duplicate data streams so as to send
data over point-to-point links over the UMTS network. Using
point-to-point links over the UMTS network is inefficient and uses
additional resources. It uses not only network resources but also
scarce radio resources. This is because the multicast data is sent
over the dedicated point-to-point links. If there are several users
in a cell, the same information is sent over several channels, one
for each user.
SUMMARY OF THE INVENTION
[0004] The present invention provides a method of sending a
multicast message to a plurality of mobile stations. The invention
involves sending to an access point of a mobile telecommunications
network a control message to assign a mobile station to a multicast
group. The multicast message is sent to the (or each) access point
having one or more associated mobile stations in the multicast
group. The (or each) access point forwards the multicast message to
its associated one or more mobile stations in the multicast group.
Furthermore, the multicast message can be an Internet Protocol (IP)
multicast message. Furthermore the multicast message can be
multicast data.
[0005] One advantage of the invention in at least some embodiments
is efficient use of core network resources, achieved by sending
only one data stream to the access network for all multicast users
in the access network. Advantageously, data can thus be sent to the
relevant radio networks without duplicating data over the core
network. Thus, multicast data can be sent down one path over the
core network to the radio network. This avoids wastage of network
resources.
[0006] The use of normal IP multicast protocols is possible.
Tailor-made applications for the mobile network are not an absolute
requirement. This makes it easy for the same terminal to be used in
the same way in a fixed IP network or wireless local area network
(WLAN) scenario.
[0007] In some embodiments, the control message is sent from an
anchor point, which is a gateway GPRS support node (GGSN), upon
receipt of a group membership instruction from the mobile station.
The instruction is preferably an internet group management protocol
(IGMP) frame.
[0008] In some embodiments, the network is a UMTS core network and
the (or each) access point is a radio network controller. It is
advantageous in this regard to adapt IP multicast protocol to the
UMTS wireless network. A mapping is provided between the IP
addresses and UMTS addresses to maximise re-use of existing UMTS
protocols, and enable joining (and leaving) IP multicast groups in
UMTS networks to use IETF standards internet group management
protocol (IGMP) messages.
[0009] In some embodiments, the mobile station is assigned to a
multicast group by sending signalling comprising a multicast access
point name (APN) as part of a create packet data protocol (PDP)
context set-up.
[0010] Preferably the control message indicates that the access
point to a mobile station is to join a multicast group so as to
receive and forward multicast messages to its associated mobile
station(s) in the multicast group. This is particularly efficient
for users in the home network.
[0011] Alternatively, the control message indicates that a radio
access bearer is to be set up for multicast messaging to the mobile
station. Preferably the anchor point is operative to set up GPRS
tunnelling protocol (GTP) tunnels for the multicast group between
the anchor point and the signalling GPRS support node (SGSN) and
between the SGSN and the access point, or to add a mobile station
identifier to a membership list for the group if the GTP tunnels
already exist. This approach is well suited to handle roaming
users.
[0012] Preferably, upon a mobile station moving to the control of a
different access point, associated multicast group membership
information is forwarded to the new access point. Preferred
embodiments thus advantageously handle mobility within a UMTS
network.
[0013] In other embodiments, the network is a second generation
GPRS core network and the access point is a signalling GPRS support
node (SGSN).
[0014] The present invention also provides a mobile
telecommunications network comprising a multicast server operative
to control the sending, to an access point of the
telecommunications network, of a control message to assign a mobile
station to a multicast group, and operative to control the sending
of a multicast message to the (or each) access point having one or
more associated mobile stations assigned to the multicast group.
The (or each) access point is operative to forward the multicast
message to its associated one or more mobile stations assigned to
the multicast group.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A preferred embodiment of the present invention will now be
described by way of example and with reference to the drawings, in
which:
[0016] FIG. 1 is a diagrammatic illustration of a preferred
UMTS/GPRS network.
DETAILED DESCRIPTION
[0017] The support of IP multicast transmissions in GPRS/UMTS core
networks can be generalised to the problem of how to support
multicast in a hierarchical tunnel-based mobility support system. A
hierarchical tunnel based mobility support system uses compulsory
tunnels from an access point that can be rearranged hop-by-hop up
to an anchor point. The access point is exemplarily the base
station controller (BSC) or radio network controller (RNC), or
another wireless or wireline access network termination node. No
assumption is here made on the nature of the access network, nor on
its ability to deliver multicast traffic using native multicast
channels or replication over unicast point-to-point channels.
[0018] The user IP packets, which include the internet group
management protocol (IGMP) messages, are carried via tunnels all
the way from the access point to the anchor point (and vice versa).
So, the problem arises that the IP connectivity between the anchor
point to the access point might not support multicast, or that the
IP multicast address might be administratively scoped--that is,
that the multicast stream available at the anchor point of
attachment to the internet might not be accessible at the visited
location (namely at the access point).
[0019] Two solutions to the problem are:
[0020] A) The use of some messages from the anchor point to the
access point that trigger the access point to join a multicast
group, multicast data being available at all possible access
points.
[0021] B) The creation of point-to-multipoint tunnels that
distribute multicast stream to the locations where mobile users
are. In this case multicast data is only available at the anchor
point and is sent down these tunnels to the access point.
[0022] We here assume that internet group management protocol
IGMPv2 is used to report multicast membership.
[0023] Access Points and intermediate nodes keep their states
related to which was the upper hierarchical level of the protocol
stack requesting them to join a multicast group. Thus, they may
enquire periodically about which of the list of multicast groups
are still active, if they have not been used for a while. The
anchor point is expected to keep its state up to date.
[0024] FIG. 1 shows the UMTS/GPRS network architecture. The new
network element is the Multicast Server/IP-multicast-capable IP
node. In FIG. 1, MT denotes the mobile termination of the core
network and TE denotes the mobile station.
[0025] The radio network controller (RNC) is the access point for,
e.g., a UMTS network in which the signalling protocol used at the
hierarchical level associated with the anchor point (e.g., the
gateway GPRS support node, abbreviated "GGSN") is GTP-C, and the
protocol at the next-lower hierarchical level is RANAP between the
serving GPRS support node (SGSN) and the RNC. "GTP" stands for GPRS
tunnelling protocol "GTP-C" stands for GTP control plane. "RANAP"
stands for radio access network application part.
[0026] For user data, the GTP user plane (GTP-U) is used from the
GGSN to the RNC. Alternatively, for second generation 2G GPRS
functionality the access point is the serving GPRS support node
(SGSN).
[0027] For a mobile station specialised for UMTS/GPRS use only, it
is possible to define a multicast access point name (APN), for
which no IP address assignment occurs. In that case, the only
purpose of the Create packet data protocol (PDP) context procedure
is to signal to the GGSN that the mobile station has joined a
multicast group. Then, one of the options A or B above is used to
manage multicast content delivery to the access point. This
provides the benefit that there is no need to send specialised IP
packets for multicast group management over the air interface (Uu,
Um).
[0028] Alternatively, the mobile node (MN) joins a multicast group
"G" by sending an unsolicited internet group management protocol
IGMPv2 membership report. The procedure in the GGSN then depends on
which of the two cases given above is used.
[0029] Case A is more suitable for intra-public land mobile network
(intra-PLMN) multicasts, whereas case B handles multicasts to
roaming users better. Of course, a packet data protocol (PDP)
context must be set up to send internet group management protocol
(IGMP) packets and must be maintained when the user is expecting
multicast data.
[0030] Case A: Triggering the Access Point to Join a Multicast
Group
[0031] The anchor point, GGSN in this case, upon detection of the
internet group management protocol (IGMP) message, sends towards
the access point serving the mobile node (or towards a
hierarchically lower anchor point serving the mobile node, which
will then forward this appropriately, until the Access point is
reached) a "join multicast group G for mobile node U" message.
[0032] In UMTS, this involves: GTP messages between the gateway
GGSN and the signalling GPRS support node (SGSN), and RANAP
messages between the SGSN and the RNC. The GGSN knows which SGSN
the user is in because there exists at least one PDP context for
the user at this GGSN, on which it detected the internet group
management protocol (IGMP) message. Hence, no home location
register (HLR) look-up is expected. The GGSN also does the mapping
between the IP address and the international mobile subscriber
identity (IMSI) for each internal user within the GPRS network. It
similarly identifies the IMSI without having to use static IP
addresses.
[0033] When the message is received at the access point (in UMTS,
for example, an RNC), the access point issues an unsolicited
internet group management protocol IGMPv2 membership report to the
next-hop router, which is expected to be multicast-capable. This
facilitates delivery of the multicast data to the access point
(e.g., RNC for UMTS).
[0034] When the mobile leaves the group without tearing down all
the PDP contexts for the active address, using IGMPv2 frames
detected at the anchor point, the anchor point repeats the process
used for joining the mobile so as to remove the mobile from the
multicast group. A similar procedure is used if the mobile node
(MN) tears down all the sessions associated with this GGSN; one
session is expected to be active at all times to receive multicast
data.
[0035] Case B: Creating Point to Point Tunnels
[0036] In this case the anchor point receives an IGMPv2 message,
and sends a message "create Multicast bearer for group `G` for
mobile node U" down the hierarchy to the access point where the
mobile joined the group. Level by hierarchical level, each node
traversed by such a message, up to and including the Access Point
where the mobile node (MN) is, establishes a tunnel with the node
immediately above it in the hierarchy, if such a tunnel did not
exist for group `G`. If such a tunnel existed, the tunnel is
reused, but the message is forwarded to the node at the next-lower
hierarchical level towards the Access point where the mobile node
is.
[0037] In UMTS, the anchor point (i.e., the GGSN) initiates the set
up of GTP tunnels to the RNC. Note that in the case of either UMTS
or GPRS, the option to indicate a request to the mobile node (MN)
with the MN initiating the set up of the tunnels/joining the group
is also possible. The quality of service (QoS) for the packet data
protocol (PDP) is also set up at that time. The QoS required for
the session may be pre-configured in the universal subscriber
identity module (USIM) or the GGSN. Alternatively, it could be
defined by the application, if an appropriate way existed for the
applications to communicate with the mobile termination (MT) and
GGSN.
[0038] As part of this PDP context set-up, a special GTP tunnel is
set up for this group between the gateway GPRS support node (GGSN)
and the signalling GPRS support node (SGSN). If a GTP tunnel
already exists for this group between the GGSN and the SGSN, the
user's international mobile subscriber identity (IMSI) is added to
the group list. A pseudo-IMSI can be associated with this PDP
context to minimise changes to existing procedures.
[0039] Handling the Radio (Iu) Interface: Radio Access Bearer (RAB)
Creation, Management and Source Radio Network Controller (SRNC)
Relocation
[0040] The signalling GPRS support node (SGSN) is responsible for
setting up of the Iu interface to the radio network controller
(RNC). For case A, the RNC need only be given an indication of the
user joining the multicast group. This can be done using a radio
access network application part (RANAP) message.
[0041] For the SGSN to set up a radio access bearer (RAB) towards
all the radio network controllers (RNCs) where users are located,
the following applies:
[0042] When a new user joins the group, and if no RAB exists
towards the RNC for this multicast group, a RAB establishment
procedure is used to create the RAB. The IMSI of the user(s)
belonging to this group must be made available to the RNC.
[0043] If an RAB already exists towards the RNC for this multicast
group, the RAB is modified to include the new user's IMSI.
[0044] The RAB establishment procedure triggers the radio network
controller (RNC) to request multicast data from the anchor
point.
[0045] For Case B, it is the responsibility of the signalling GPRS
support node (SGSN) to duplicate the packet and send it on each of
the RABs. Note that this can be done at the GPRS tunnelling
protocol (GTP) level without having to look at the user IP
packet.
[0046] User Mobility
[0047] When a mobile moves, the multicast groups status associated
with it is relocated to the new access point. The old access point
may leave the multicast group G if the mobile node (MN) was the
only one that had joined a multicast group, or it may keep the
membership active if other users were members of multicast group G
at the access point.
[0048] When a user moves between serving GPRS support nodes
(SGSNs), the user context moved between the SGSNs includes the
groups to which the user belongs. This information is carried in
the appropriate inter-serving SGSN GTP mobility messages depending
on the user state--either idle or Iu-connected. An update packet
data protocol (PDP) context is initiated by the new SGSN towards
the gateway GPRS support node (GGSN) to update the serving SGSN to
which the user belongs.
[0049] Upon source radio network controller (SRNC) relocation, the
groups to which the user belongs are passed by the serving GPRS
support node (SGSN) to the transmit radio network controller
(TRNC). If the new radio network controller (RNC) does not receive
multicast data for such a group, a new radio access bearer (RAB)
must be created if none exist towards the RNC (for Case B), or else
the RNC must send an unsolicited internet group management protocol
IGMPv2 membership report to the next-hop router (for case A).
* * * * *